Prosthesis device

ABSTRACT

A prosthesis device having a tension element fastened to a tensile force brace, which drives a movable component of a prosthesis device upon applying a tension force, wherein a sensor device is allocated to the tension element which detects the actuation of the tension element and activates a motor allocated to the movable component.

The invention relates to a prosthesis device with a tensioning elementwhich is fastened to a body harness and which drives a movable componentof the prosthesis device when a tensile force is applied. The prosthesisdevice is configured in particular as a prosthetic arm.

Prostheses replace missing or lost limbs. In addition to purely cosmeticprostheses which simply replace the form of the missing limb, mostmodern prostheses attempt to replace one or more functions of the limbor to provide a functionality similar to that of a natural limb.

Lower-limb prostheses can be configured as prosthetic feet, which arefastened to a lower leg socket. More complex prostheses replace a kneejoint, including single-axis blocking knee joints, multi-link kneejoints, computer-controlled passive knee joints and driven knee jointsof varying degrees of complexity. There are additionally prosthesisdevices for patients with exarticulation of the hip.

The natural upper extremities are able to perform a large number ofmovements. The gripping and holding function of the hand, variousrotation movements of the forearm and the high degree of mobility in theshoulder joint permit a large number of actions and movements, which canbe simulated only with difficulty in an artificial system. In the caseof prosthesis devices of the upper extremity, there are also differentdegrees of complexity ranging from simple hooks and grippers to drivenprosthetic hands or motor-driven, myoelectric-controlled prostheticarms.

Alongside highly complex, computer-controlled, sensor-based prosthesisdevices, there is still a need for comparatively simple mechanicalprosthesis devices which are actuated by what are called body harnesses.In these cases, a movable component of a prosthesis of the upperextremity is actuated by a shoulder movement, for example a movement ofthe shoulder of the contralateral and intact limb. A movable componentcan be moved in a direction either against the force of gravity oragainst an opposing force, e.g. a spring force. If active functions of aprosthesis device are triggered exclusively via a force by means of abody harness, such prostheses are referred to as body-poweredprostheses. Compared to prostheses with electric drives, body-poweredprostheses are directly controllable and have proprioceptive feedback.

A common application of body-powered prostheses is one in which agripper or gripping element is opened counter to an opposing force, inparticular a spring force, via the body harness. The opposing force canbe applied via compression springs, tension springs or rubber rings, orpneumatically, or in some other way, and thus generates the grippingforce. Since a high gripping force is advantageous in many activities,comparatively strong springs or rubber rings or force-generatingelements are fitted. This opposing force has to be overcome when openingthe gripper, i.e. applied by the patient by means of the body harness.Permanently working against the comparatively high opposing forces canlead to early fatigue or health problems for the patient.

DE 26 39 143 C2 relates to a gear for an orthosis or prosthesis, forconverting a rotation movement of a drive unit into a reciprocatingmotion of a moved part of an orthosis or prosthesis. The gear has arotatably mounted structural part, which is coupled to the drive unitand has a thread, and, engaging with the structural part, a gear partguided non-rotatably on the housing. The structural part consists of ahollow cylinder open at one end, with an inner thread and an outerthread with oppositely directed pitches. One end of a cable pull orchain pull is fixed to a screw spindle interacting with the innerthread, and the other end is fixed to a sleeve interacting with theouter thread. The gear is configured in the manner of a double spindle,the effect of which is that the tensile forces acting on the cable pullor chain pull are substantially constant over the entire displacementpath.

DE 821 690 B relates to a prosthetic hand with a hollow hand body inwhich a cam disk is arranged. By way of rods and tensioning brackets, arotation of the cam disk is converted into a movement of the fingers inorder to open or close the hand.

DE 26 07 499 C3 relates to a drive device for the fingers of anartificial hand, in which a movable thumb and at least one finger movedin an opposite direction to the thumb are driven by motor with the aidof a self-locking gear. A worm is in direct engagement with toothedwheels secured to the movable fingers and to the thumb. The toothedwheels mesh with the worm at diametrically opposite sides, wherein theworm is driven with the aid of a reversible gear.

U.S. Pat. No. 4,604,098 A relates to a prosthetic arm having a forearmpart, an elbow joint with locking elements and engaging elements toprevent bending of the elbow, and an upper arm part connected to theforearm part via the elbow joint. The forearm part is moved relative tothe upper arm part about the elbow joint via a motor. The locking meanscan be disengaged via an unlocking mechanism in order to permit bending.The bending movement and the locking or unlocking are controlledelectronically.

The object of the present invention is therefore to make available aprosthesis device which ensures fatigue-free work and places less strainon the patient.

According to the invention, this object is achieved by a prosthesisdevice having the features of the main claim. Advantageous embodimentsand developments of the invention are disclosed in the subclaims, thedescription and the figures.

In the prosthesis device according to the invention, with a tensioningelement which is fastened to a body harness and which drives a movablecomponent of the prosthesis device when a tensile force is applied,provision is made that the tensioning element is assigned a sensordevice which detects the actuation of the tensioning element andactivates a motor assigned to the movable component. The sensor devicedetects whether and how tensile forces are applied to the tensioningelement via the body harness. The sensor device measures the extent ofthe applied tensile force. The sensor device forwards thecorrespondingly generated sensor signals to a control device, which iscouple to the sensor device. A motor is activated via this controldevice, i.e. started up according to the sensor signals, in order todrive the movable component or at least to support the intended movementof the movable component. Direct feedback to the user of the prosthesisdevice is provided via the body harness, such that the advantages of aconventional body-powered prosthesis are retained. At the same time, theforce to be applied by the body harness is reduced, since only a reducedforce has to be applied in order to actuate the movable componentcounter to the force of gravity or counter to the spring force, becausethe motor supports the intended movement. In contrast to prostheses thatare operated exclusively by external force, it is advantageous if anactuating force is still applied to the movable component via the bodyharness. Similarly to servo-assisted steering, the intended movement iseffected via the tensioning element; only the force to be applied by thepatient is reduced.

The movable component can preferably be configured as a mechanicalgripping element or gripper or as a joint component. The mechanicalgripper is preferably opened counter to an opposing force, in particulara spring force, and, when the tensile force and the motor support cease,the mechanical gripper closes, such that no further force then has to beapplied for secure gripping or fixing of an object. The holding force isexerted by the pretensioning or the force-applying element. Inprinciple, it is also possible and provided for that the closuremovement of the gripper is performed by the body harness and thetensioning element, according to the invention with the support of amotor. When the tensile force and the motor support cease, the gripperis then opened as a result of a spring force, in an opposite embodimentopened counter to a spring force. Alternatively or in addition to apurely mechanical gripper, provision is made that a joint component ofthe prosthesis device is also driven in such a manner. A movement of theprosthesis component in a defined direction, whether counter to a springforce or counter to the force of gravity, is provided. For example,prosthesis components can be moved about a pivot axis counter to springforces, wherein the spring forces keep the prosthesis component in astarting position. Depending on the direction of force, the prosthesiscomponent can then be pivoted or rotated in one or other direction. Themechanical gripper can have two or more hook-shaped gripping elementsand can in particular be configured itself as a hook. In addition to agripper with two fingers, it is also possible to provide a prosthetichand as gripper.

In a development of the invention, provision is made that the supportforce applied by the motor is proportional to the tensile force appliedby the tensioning element. This ensures direct proprioceptive feedback;the more force is applied via the body harness, the greater the tensileforce applied to the figurative component and the greater the supportforce additionally applied via the motor. The stated advantages of thedirect feedback are seen in particular in the closure of the mechanicalgripper by the tensile force and the motor support. The pressure pointand the grip point are likewise adjustable.

The motor is preferably coupled to the tensioning element and/or to themovable component via a gear. The interposition of one or more gearsmakes it possible to use small, fast and light motors, which isparticularly advantageous as regards the preferred use in upper-limbprostheses, since there is little space available in these for fittingmotors and energy accumulators. As gears, it is possible to use cablewinding gears, toothed belt gears, toothed wheel gears, drum gears,friction gears or planetary gears. In particular, cable winding gearsare advantageously used since, in conventional mechanical grippers, theforce transmission takes place from the contralateral shoulder to themechanical gripper via a cable pull, if appropriate with deflectionrollers.

The geared transmission and also the proportionality factor areadvantageously adjustable in order to permit adaptation to differenttypes of use. It is likewise advantageous if the proportionality factorof the support force by the motor is adjustable, likewise the forceamplification or the support performance by the motor. Thus, if supportis not required, the motor can be supplied with less energy oruncoupled, as a result of which the duration of use of the prosthesisdevice is longer, since only as much support energy as is needed issupplied.

In a development of the invention, provision is made that the movablecomponent is loaded with a spring force which counteracts the tensioningelement and/or the motor. It is thereby possible to influence theopening or closing of the gripper, or the flexion or extension of thejoint component, and, particularly in the case of a gripper, to permit adefined holding force without additional movement or additional input ofenergy. In the case of joint devices, the components can thereby beplaced in relation to each other in a preferred setup, which can bechanged only by applying a force starting from a defined thresholdvalue.

The sensor device can have a force sensor in the tensioning element orin a deflection roller, in order to be able to provide a suitableadditional force which, for example, is proportional to the forceapplied by the user. The proportionality factor does not have to belinear across the force; the additional force via the motor can beraised more than proportionally as the force increases. It is alsopossible that the maximum applied force is limited, i.e. that the sum ofthe force transmitted to the movable component via the tensioningelement is limited to a maximum value.

In one embodiment of the invention, the sensor device or the forcesensor is configured as a force-measuring bolt. The sensor is preferablyconfigured as a force-measuring bolt inside the tensioning element, suchthat simple determination of the force acting inside the tensioningelement is permitted. The force can be measured via a signal amplifier,and the force additionally to be supplied by the motor can be appliedproportionally to the tensile force. In addition to a linearproportionality, it is also possible to provide progressive ordegressive proportionalities in order, for example, to provide veryconsiderable support when particularly high forces are applied by thetensile force.

Alternatively or in addition to a direct arrangement of the sensorinside the tensioning element, a force-measuring device can also bearranged in a deflection roller or on a gear element, in order there todetect the tensile force applied via the tensioning element or the bodyharness and to activate the motor.

The motor can be assigned to the tensioning element and/or to themovable component via a coupling, such that, if the motor fails or theenergy accumulator becomes depleted, the movable component can still beactuated as usual by the tensioning element. The motor can thus beswitched on between the tensioning element and the movable component orif appropriate uncoupled therefrom. The coupling can be embodied, forexample, as a centrifugal coupling or a spring-loaded release coupling.

By way of a coupling, it is also possible for the prosthesis device tohave a modular construction, that is to say a conventional body-poweredprosthesis with an additional component in the form of the motor withthe control device can be offered as an accessory component in order topermit an additional and improved functionality of the prosthesisdevice.

The movable component, in particular the movable gripper, is fastenedexchangeably on the prosthesis device, in order to be able to providedifferent functionalities for different actions.

The tensioning element can be configured as a cable pull or strap whichis actuated via the body harness. The tensioning cable or tensioningelement can be guided in a cable sheath or sleeve, wherein the endpieceis free and is fastened via a deflection roller, and if appropriate asupport roller, on the movable component, in particular the mechanicalgripper.

The tensioning element can be routed at least partially inside aprosthesis socket, wherein the tensioning element is adapted to therespective patient or user by an orthopedist. Both the length of thetensioning element and also the gear ratios and amplifications areadapted individually to the respective patient and are adjustable.

The motor can act on the tensioning element and thereby increase thetensile force applied to the movable component via the tensioningelement, i.e. use the tensioning element as the only element fortransmitting force to the movable component. Alternatively, the motorcan be coupled to the movable component, separately from the tensioningelement, and can be coupled directly to the movable component forexample via a toothed wheel gear or a friction gear, if appropriate withan interconnected freewheel. The force transmission from the motor tothe movable component does not then take place via the tensioningelement, but separately, as a result of which no changes have to be madeto the structure of the original prosthesis device. Only the sensordevice has to be assigned to the tensioning element, and the supportdevice with motor, and if appropriate with gear and controller, has tobe coupled mechanically to the movable component in a force-transmittingmanner.

Illustrative embodiments of the invention are set out below and areexplained in more detail with reference to the attached figures, inwhich:

FIG. 1 shows a movable component in the form of a gripper; and

FIG. 2 shows a schematic illustration of the prosthesis device.

A movable component 1 in the form of a mechanical gripper, configured asa hook, is shown on its own in FIG. 1. The mechanical gripper 1 has amain body 2, at one end of which a fastening device 3 in the form of athread is arranged or formed for the purpose of fixing to a prosthesissocket (not shown). Two fingers 10, 20, shaped like hooks and configuredto grip objects (in the form of a pen in FIG. 1), are formed at the endof the main body 2 opposite the fastening device 3. A first finger 20 isfastened rigidly to the main body 2, and the second finger 10 is mountedpivotably on the main body 2, wherein the pivot axis (not shown) isconfigured in such a way that the second finger 10 can be moved awayfrom the first finger 20, such that a space between the two fingers 10,20 can be made larger or smaller. The movement of the second finger 10away from the first finger 20 takes place counter to an opposing forcewhich allows the two fingers 10, 20 to bear on each other in thenon-actuated state. The opposing force is exerted via a rubber ring 4which is placed around a base 11, 21, respectively, for the secondfinger 10 and first finger 20. The rubber ring 4 is placed in groovesand is thus mounted exchangeably on the two bases 11, 21. Depending onthe intended use, and on the required holding force that is to beexerted between the two fingers 10, 20, different rubber rings 4 can beplaced in the groove. If only a low holding force is required, aresilient rubber ring 4 is inserted; if a high holding force isrequired, a more stable rubber ring 4 is used that has lessextensibility and elasticity and therefore greater resistance to anexcursion.

The fingers 10, 20 can be fastened to the respective base 11, 21 in anexchangeable manner, for example screwed in, or inserted in some otherway and fixed with form-fit engagement.

To move the second finger 10 away from the first finger 20, a tensioningelement 5 is fastened to a third finger 12, which is coupled rigidly tothe second finger 10. The tensioning element 5 is configured in the formof a tensioning strap or cable or a cable pull and is mounted withform-fit engagement on the third finger 12, in a groove 6 formed in thelatter. The groove 6 extends along the proximal side of the third finger12, i.e. the side directed toward the prosthesis socket, and permits achange of the leverage when force is transmitted from the tensioningelement 5 to the second finger 10. The farther outward the tensioningelement 5 is moved, the greater is the lever travel, as a result ofwhich the force that has to be applied is reduced and at the same timethe opening travel between the fingers 10, 20 is reduced. The thirdfinger 12 is coupled to the second base 11 and protrudes from thelatter, such that the second base 11 and therefore also the secondfinger 10 are pivoted about the pivot axis when a tensile force isapplied by the tensioning element 5. The pivot axis is orientedsubstantially perpendicularly with respect to the substantially circularmain surfaces of the disk-like main body 2. When the tensioning element5 is pulled, the third finger 12, and with its also the second finger10, moves downward in the direction of the arrows; when the tensileforce is reduced, the third finger 12, and with it also the secondfinger 10, moves upward in the direction of the arrows, since the rubberring 4 exerts the corresponding opposing force. The object to begripped, a pen in the illustrative embodiment shown, is held between thefirst finger 20 and the second finger 10 and can be laid against thethird finger 12.

In the case of a body-powered prosthesis, the actuation of thetensioning element 5 can take place exclusively via a movement of a partof the body, for example the shoulder of the treated or intact arm.

FIG. 2 shows the prosthesis device in a schematic illustration. A bodyharness 7, which is coupled to a prosthesis socket 8, is fitted on apatient, who is indicated on the left in the schematic illustration. Thebody harness 7 is fastened to the contralateral, intact shoulder andguided in the form of a loop around the shoulder. On the back, in theregion of the upper thoracic vertebra, the loop is secured in a ring, towhich a tensioning element 5 in the from of a tensioning strap isfastened. When the intact shoulder is moved forward, this has the effectthat a tensile force is applied to the tensioning element 5. Thetensioning element 5 is guided along the upper arm on the treated side,such that the tensioning element 5 is guided inside the prosthesissocket 8. In the embodiment shown, the tensioning element 5 isconfigured initially as a strap which, inside the prosthesis socket 8,is then coupled to a cable-shaped tensioning element 5, for example awire pull, a cord, the core of a Bowden cable or the like, ortransitions into a tensioning element 5 of such a kind.

A support device 50, shown schematically and on an enlarged scale, isarranged inside the prosthesis socket 8. The support device 50 can beconstructed as a module and can have a housing 51 inside which thecable-shaped tensioning element 5 coming from the body harness 7 isguided. The tensioning element 5 is guided around a deflection roller52, which is coupled to a sensor device in the form of a force-measuringbolt. From the deflection roller 52, the tensioning element 5 is guidedby way of a support roller 54, and from there it is fastened to thethird finger 12 of the movable component 1. FIG. 2 shows an alternativeembodiment of the movable component in the form of a mechanical gripper1 in which the main body 2 is not shaped as a circular disk and in whichthe element 4 generating the opposing force is not configured as arubber ring but instead configured with a triangular contour and as atension spring. When the tensioning element 5 is subjected by the bodyharness 7 to a tensile force in the direction away from the mechanicalgripper 1, the deflection roller 52 is rotated, likewise the supportroller 54, and the two fingers 10, 20 are thereby moved away from eachother.

An electric motor 60 with a drive shaft 61 is arranged inside thesupport device 50. The motor 60 is supplied with energy via anelectrical energy accumulator 70. The motor 60 is assigned a controldevice 80, by which the motor 60 is activated or deactivated. In theillustrative embodiment shown, the deflection roller 52 is assigned asensor device 81 in the form of a force-measuring bolt. When a tensileforce is applied to the tensioning element 5, the deflection roller 52is subjected to a torque and to a force which is measured via the sensordevice 81. The signal is sent to the control device 80 via a signalamplifier 82. When a tensile force within the tensioning element 5 isdetected at the deflection roller 52, the motor 60 is activated via thecontrol device 80. The drive shaft 61 is driven. An output shaft 62 iscoupled to the drive shaft 61 via a cable winding gear 90. The driveshaft 61 winds up a coupling cable and thereby rotates the output shaft62, which is coupled to the support roller 54 via a coupling 63. Thecoupling 63 can be configured as a centrifugal coupling or spring-loadedtoothed-wheel coupling. It is likewise possible that the coupling has aserrated spur toothing which is oriented such that force is transmittedonly in the direction of support of the tensile force of the tensioningelement 5.

In the illustrative embodiment shown, the support roller has to rotateto the left in order to open the mechanical gripper 1; the flanks of theserrated spur toothing would then fall away to the right. Instead of acable winding gear as shown, it is possible for toothed wheel gears,toothed belt gears, drum gears or friction gears or planetary gears tobe formed between the motor 60 and the support roller 54. By means ofthe different diameters of the drive shaft 61 and of the output shaft62, it is possible to achieve different transmission ratios of the cablewinding gear 90, and adaptation can easily be achieved by exchanging therespective shafts or the drums on the respective shafts 61, 62 and/orthe support roller 54.

The support force applied by the motor 60 can be adjusted via thecontrol unit 80. The adjustment can be made according to the planned useof the mechanical gripper 1 or according to the personal preference ofthe user.

Instead of a force-measuring bolt 81 on the deflection roller 52, it isalso possible and provided for that the sensor device 8 is arrangedalong the course of the tensioning cable 5, for example in the form of atensile force sensor, which determines the tensile force effective inthe tensioning element 5. The sensor data can be transmitted to thesignal amplifier 82 wirelessly or also by wire. Along most of itslength, the tensioning element 5 can be routed through a sheath in orderto avoid chafing of the tensioning element 5 on the skin or on theclothes of the user.

The support device 50 can be configured as a module and simply fittedonto an existing body-powered prosthesis. The tensioning element 5simply has to be placed around the deflection roller 2 and the supportroller 54, which means only a slight lengthening of the tensioningelement 5 compared to direct fastening on the mechanical gripper 1.Should the energy accumulator 70 be empty or the motor 4 have a defect,the prosthesis device can continue to be used without any greatlimitation in respect of its function; only the comfort is reduced.

Instead of force being applied by the motor 4 via the tensioning element5, in an alternative embodiment the drive is coupled directly to themovable second finger 10. The support device 50 can be integrated in themain body 2 and coupled in a force-transmitting manner to the movablefinger 10 via a gear arrangement, for example a friction gear or atoothed wheel gear with a suitable coupling 63. If a tensile force isthen detected by the sensor device 81, which can also be arrangeddirectly in the tensioning element 5, the sensor device 81 can transmitthis by cable or wirelessly to the signal amplifier 82 of the controldevice 80, whereupon the motor 60 is then activated. In this way, it ispossible to dispense with loading of the tensioning element 5 by theadditionally applied motor force. Modifications to the attachment of thetensioning element 5 to the mechanical gripper 1 are not necessary. Thesupport device 50 is provided as a separate mechanical component, in theform of a prefabricated module with the motor 60 and the integratedcontroller 80 together with the energy accumulator 70, and simply has tobe fastened in the main body 2 or on the main body 2. The force of themotor 60 is then transmitted via a suitable coupling 63 in order todrive the movable finger 10. The extent of the force which is to beapplied, likewise the duration for which it is to be applied, aredefined by the tensile forces that are determined in the sensor device81. It is possible to adopt a linear proportionality between the tensileforce applied via the tensioning element 5 and the additionally providedmotor force; alternative proportionality factors are possible. A commonaspect of both embodiments is that the functionality of the mechanicalgripper 1 is maintained in the event of a failure of the support device50.

1. A prosthesis device, comprising: a body harness; a tensioning elementwhich is fastened to the body harness and which drives a movablecomponent of the prosthesis device when a tensile force is applied; asensor device assigned to the tensioning element to detect actuation ofthe tensioning element and activate a motor assigned to the movablecomponent.
 2. The prosthesis device as claimed in claim 1, wherein themovable component is configured as a mechanical gripper or jointcomponent.
 3. The prosthesis device as claimed in claim 1, wherein asupport force applied by the motor is proportional to the tensile forceapplied by the tensioning element.
 4. The prosthesis device as claimedin claim 1, wherein the motor is coupled to at least one of thetensioning element and the movable component via a gear.
 5. Theprosthesis device as claimed in claim 4, wherein the gear is configuredas a cable winding gear, toothed belt gear, toothed wheel gear, drumgear, friction gear or planetary gear.
 6. The prosthesis device asclaimed in claim 4, wherein a geared transmission and a proportionalityfactor of the gear are adjustable.
 7. The prosthesis device as claimedclaim 1, wherein a support force provided by the motor is adjustable. 8.The prosthesis device as claimed in claim 1, wherein the movablecomponent is loaded with a spring force which counteracts at least oneof the tensioning element and the motor.
 9. The prosthesis device asclaimed in claim 1, wherein the sensor device has a force sensor in thetensioning element or in a deflection roller.
 10. The prosthesis deviceas claimed in claim 1, wherein the force sensor is configured as aforce-measuring bolt.
 11. The prosthesis device as claimed in claim 1,wherein the motor is assigned to at least one of the tensioning elementand the movable component via a coupling.
 12. The prosthesis device asclaimed in claim 1, wherein the motor drives the tensioning element orseparately drives the movable component.
 13. A prosthesis device,comprising: a body harness; a movable component; a motor operable toapply a support force to the movable component; a tensioning elementwhich is fastened to the body harness and which drives the movablecomponent when a tensile force is applied; a sensor device assigned tothe tensioning element to detect actuation of the tensioning element andactivate the motor.
 14. The prosthesis device as claimed in claim 13,wherein the movable component is configured as a mechanical gripper orjoint component.
 15. The prosthesis device as claimed in claim 13,wherein a support force applied by the motor is proportional to thetensile force applied by the tensioning element.
 16. The prosthesisdevice as claimed in claim 13, further comprising a gear, the gearcoupling the motor to at least one of the tensioning element and themovable component.
 17. The prosthesis device as claimed in claim 16,wherein the gear is configured as a cable winding gear, toothed beltgear, toothed wheel gear, drum gear, friction gear or planetary gear.18. The prosthesis device as claimed in claim 16, wherein the gearincludes an adjustable geared transmission and an adjustableproportionality factor.
 19. The prosthesis device as claimed claim 13,wherein the support force provided by the motor is adjustable.
 20. Theprosthesis device as claimed in claim 13, wherein the movable componentis loaded with a spring force which counteracts at least one of thetensile force of the tensioning element and the support force of themotor.